Electrical signal noise is any unwanted electrical or magnetic interference that affects other electrical signals and/or corrupts electrical data. There are many causes for electrical signal noise. The different types of electrical noise include conducted emissions, radiated emissions, conducted susceptibility, and radiated susceptibility. Electrical signal noise typically occurs over a wide frequency spectrum resulting from alternating currents and voltages. Over the years, there have been many proposed methods and circuit arrangements aimed at reducing electrical signal noise in electrical systems.
U.S. Pat. No. 4,904,968 appears to describe a particular circuit board configuration for reducing signal distortions that includes use of a ground plane.
A via is a hole, lined with a conductive material, that extends from one layer of a printed circuit board to a different layer. The via can be used to simply make a connection between desired layers of the printed circuit board or can be used to provide an electrical connection between a desired layer and a mounted electrical component. Vias can be formed by drilling or etching through the selected dielectric layer(s) and then plating the hole with a conductive material so as to provide the desired electrical connection between the associated layer(s) and circuit component.
Vias, themselves, can lead to noise problems in printed circuit boards where the vias carry electrical signals. In printed circuit boards having connecting vias, stitching capacitors have been introduced between conductive and ground planes for noise reduction. One example of stitching capacitors is found in U.S. patent publication 2006/0076160A1.
U.S. Pat. No. 7,154,356 appears to describe a radio frequency (“RF”) circuit board topology having inter-connective layers including a signal conductor via surrounded by a plurality of ground vias so as to affect the overall characteristic impedance of the interconnection structure.
In an IEEE paper entitled “The EMI (electromagnetic interference) benefits of ground plane stitching in multi-layer conductive bus stacks” by Ye et al., (Paper No. 0-7803-5677-2/00 pages 833-838, 2000), there is described a printed circuit board arrangement having multiple ground planes. The ground planes are stitched together at the periphery of the board using closely spaced vias so as to reduce the level of radiation from other EMI fields. The paper focuses on the impact of ground plane stitching on radiated EMI.
In a vehicle environment, electrical signal noise produced by electrical circuitry can be disruptive to other electrical and electronic devices of the vehicle such as the vehicle's radio.